Two types of projection display systems are digital light processor (DLP) systems, and liquid crystal display (LCD) systems. Applications for such display systems include multi-projector tiled projection and multi-projector superimposed projection. Many imaging applications, including multi-projector display systems, use a camera for measurement purposes. In order to accurately measure properties of the display system, the camera should first be calibrated. Image sensor analog-to-digital converters (ADCs) typically have dark current effects that may lead to non-zero readings even when capturing absolutely no photons. For the same ambient conditions, the sensor readings may vary pixel-to-pixel, but generally not over time. Hence, fixed pattern noise occurs that can corrupt each and every captured image, thereby affecting every measurement for the imaging application. Furthermore, with typical image sensors, the fixed pattern noise may vary as a function of exposure.
In addition to the problem of fixed pattern noise, some imaging applications capture images from different exposures and integrate them together for high dynamic range imaging. In this case, it is desirable to know the camera transfer curve for an accurate measurement. Moreover, many of the calibration steps may be performed using different exposures, and thus it may be desirable for the camera transfer curve to be estimated in advance.
For many imaging applications, including multi-projector display systems, it is desirable to accurately estimate the display gamma of the display devices (e.g., projectors). It is known to use a spectrophotometer to measure the display gamma of a display device. However, this approach is expensive, slow, and localized to a particular spot on the screen. It is also typically impractical to use a spectrophotometer in the field.